UltraLinux has ran on a 14 CPUs machine (see the dmesg output) and on a Starfire E10000 with 24 CPUs (see the dmesg output).

The SparcStation 10 and SparcStations 20 are SMP capable machine and according to the FAQABOSS the following combinations are known to work:

2xSM40 ( model 402 )

2xSM41 ( model 412 )

2xSM51 ( model 512 )

2xSM512 ( model 514 )

2xSM61 ( model 612 )

2xSM71 ( model 712 )

2xSM81 ( model 812 )

And, as stated earlier, CPU modules in SparcStations 10 and can run a different clock speeds, the following ones _SHOULD_ work:

2xSM50

SM41, SM51

SM41, SM61

SM51, SM61

SM71, SM81

How does it performs? Well, it is fast, really fast. Some of the java Demos can run faster on a dual HyperSparc 125Mhz 128MB ( ywing ) than on a dual celeron BP6 433@433Mhz 192MB ( calimero ). The same applies for the Gimp. When it comes to compiling calimero runs faster than ywing. Both computers running 2.2.16 kernel and calimero's hard disk subsystem is full SCSI.

One important detail when you plan to have different CPU modules in your computer is to have the same kind of modules, you cannot mix SuperSparc and HyperSparc for example, but you can have an odd number of CPUs, for example 3. They are said to be able to run modules at different clock speed as written in this article form AcesHardware , but I have not witnessed it. (Lionel, trollhunter Bouchpan-Lerus-Juery)